JP2006080499A - Light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the luminance of a light-emitting device provided with Ca solid solution alpha sialon phosphor activated by Eu. <P>SOLUTION: An alpha sialon phosphor 7, whose inflection point is in the blue wavelength range of excitation spectrum in which an emission peak wavelength is measured as a monitor wavelength, and a blue light-emitting diode element 5 whose emission peak wavelength is in a range of ±3 nm with the inflection point as a center, are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light-emitting device including a blue light-emitting diode element and a phosphor that absorbs blue light emitted therefrom and emits yellow fluorescence.

  Conventionally, a light emitting diode element that emits short-wavelength light such as blue light, and fluorescence that is excited by absorbing part or all of the light emitted from this light-emitting diode element and emits fluorescence of longer wavelength such as yellow A white light emitting diode (light emitting device) using a substance is known.

  An example of such a white light emitting diode is a compound semiconductor blue light emitting diode element and yttrium aluminum garnet activated with cerium that absorbs blue light emitted therefrom and emits yellow fluorescent light that is a complementary color of blue. Examples include (Yttrium Aluminum Garnet: YAG) phosphors (for example, see Patent Document 1).

  FIG. 7 is a diagram showing an excitation spectrum and an emission spectrum of a YAG phosphor activated by Ce (cerium), which is one of the phosphors as described above.

  The emission spectrum on the right side of the figure is measured with an excitation wavelength of 460 nm, which is the emission wavelength of a commonly used blue light-emitting diode element.

  The emission monitor wavelength of the excitation spectrum on the left side of the figure is the emission peak wavelength of 563 nm of the above emission spectrum.

  A white light emitting diode can also be realized by using an alpha sialon phosphor instead of the YAG phosphor activated by Ce.

As an example of the alpha sialon phosphor used in such a white light emitting diode, there is a Ca (calcium) solid solution alpha sialon phosphor activated by Eu (see, for example, Patent Document 2).
Japanese Patent No. 2927279 JP 2002-363554 A Xiao Zhang and Xingren Liu, J. Electrochem. Soc., Vol. 139, No. 2, February 1992, pp. 622-625.

  However, the light emitting device using the above-mentioned alpha sialon phosphor has the following problems to be solved.

  FIG. 8 is a diagram showing an emission spectrum of a Ca solid solution alpha sialon phosphor activated by Eu when the excitation wavelength is 450 nm and when it is 460 nm. As shown, the emission intensity is higher at 450 nm. The emission intensity is weaker at 460 nm.

  In other words, in this sialon phosphor, 460 nm, which is the emission wavelength of a commonly used blue light-emitting diode element, is not optimal as an excitation wavelength and needs to be reexamined.

A first aspect of the present invention includes a blue light emitting diode element and a calcium solid solution sialon phosphor activated by divalent europium ions, and the inflection point of the excitation spectrum of the calcium solid solution sialon phosphor emits light. Provided is a light emitting device which is in a blue wavelength region of an excitation spectrum measured using a peak wavelength as a monitor wavelength, and in which a light emission peak wavelength of a light emitting diode element is within a range of ± 3 nm centering on an inflection point.
According to a second aspect of the present invention, in the first aspect, the inflection point corresponds to a transition from a 4f ⁷ ( ⁸ S _7/2 ) ground state to a 4f ⁶ ( ⁷ F ₃ ) 5d excited state. A light emitting device that appears at an excitation wavelength is provided.
According to a third aspect of the present invention, there is provided the light emitting device according to the second aspect, wherein the inflection point is 449 nm to 450 nm.
A fourth aspect of the present invention, in a first aspect, the composition of calcium dissolved sialon phosphor, the general formula _{Ca x Si 12- (m + n} ) Al (m + n) O n N 16-n: with ^{Eu 2+} _y Provided is a light-emitting device represented by 0.6 ≦ x ≦ 1.0 and 0.05 ≦ y ≦ 0.10, and the light emission peak wavelength of the light-emitting diode element is in a range of 450 ± 3 nm.

  ADVANTAGE OF THE INVENTION According to this invention, the brightness | luminance of a light-emitting device provided with Ca solid solution alpha sialon fluorescent substance activated by Eu can be improved.

<Ca Ca-Solued Alpha Sialon Phosphor in the Present Invention>
The present invention relates to a light emitting device with improved brightness, which is realized by the Ca solid solution alpha sialon phosphor of the present invention. Therefore, before describing the light emitting device, the Ca solid solution alpha sialon phosphor of the present invention will be described.

  As means for solving the above problems, first, an excitation spectrum is measured, and a wavelength having a sufficiently strong excitation intensity at or near its peak wavelength is selected as the excitation wavelength.

  On the other hand, the excitation wavelength cannot always be determined simply from the shape of the excitation spectrum of the phosphor. For example, when the excitation wavelength is short, there is a problem that the resin used for sealing becomes severely deteriorated.

  Therefore, it is necessary to determine an appropriate excitation wavelength in consideration of various factors.

  However, as a result of the research activities of the present inventors, the inventors have discovered a very rare feature that the excitation spectrum of the Ca-soluble alpha sialon phosphor activated by Eu is not normally within the range that can be predicted by those skilled in the art. .

  FIG. 5 is a diagram showing excitation spectra of 6 samples out of 8 samples used in this experiment.

  As a feature common to all of these six samples, an inflection point is seen at a wavelength of 450 nm.

  On the long wavelength side from this inflection point, the excitation intensity decreases rapidly. On the other hand, there is no commonality in the excitation spectrum shape on the shorter wavelength side than the inflection point. In samples A1 and A2, the inflection point of 450 nm is the excitation peak wavelength, and the excitation intensity decreases as the wavelength becomes shorter. On the other hand, the sample B1 has a flat excitation spectrum in a very wide range, and the samples B2, B3, and B4 have a reversed result that excitation wavelengths are stronger at wavelengths of around 400 to 410 nm.

Hereinafter, each sample will be described.
Samples A1 and A2 are in the same process and the same lot up to the sintering process described later, and are different only in that they are classified by the particle diameter in the post-processing.

Activated calcium divalent europium of the present invention (Eu) (Ca) solid solution alpha SiAlON phosphor has the general formula _{Ca x Si 12- (m + n} ) Al (m + n) O n N 16-n: Eu 2+ _y = x = 0.75, m = 1.7499, n = 0.87495, y = 0.0833.

Alpha silicon nitride (αSi ₃ N ₄ ), aluminum nitride (AlN), calcium carbonate (CaCO ₃ ), and europium oxide (Eu ₂ O ₃ ) were used as starting materials, and these were weighed and mixed.

  Sintering is carried out in the form of a powder, and is thoroughly loosened using a mortar in the state of a dry powder. It was in a powder state.

  In addition, a gas pressure sintering apparatus is used for this sintering, and the sample is placed in a container with a boron nitride lid, which is accommodated in the gas pressure sintering apparatus, and gas is supplied at 0.5 MPa in a nitrogen atmosphere. Pressure sintering was performed. The sintering temperature at this time was 1700 ° C., and the holding time at the sintering temperature was 24 hours.

  After sintering, when it was taken out from the apparatus, it was broken into a powder by applying a slight force on the mortar.

  Next, only particles having a particle size of 63 μm or less were classified and classified using a stainless steel test mesh sieve having a nominal aperture of 63 μm in accordance with JIS Z 8801. This was further classified and classified with a nominal opening of 45 μm, and the larger one was designated as sample A1 and the smaller one as sample A2.

  Samples B1 to B4 are also in the same process and the same lot up to the sintering process, and only the post-processing is different. The composition was set to x = 0.75, m = 1.499, n = 0.87495, and y = 0.0833 as in the samples A1 and A2.

Alpha silicon nitride (αSi ₃ N ₄ ), aluminum nitride (AlN), calcium carbonate (CaCO ₃ ), and europium oxide (Eu ₂ O ₃ ) were used as starting materials, and these were weighed and mixed.

  Sintering is carried out in the form of a powder, and is thoroughly loosened using a mortar in the state of a dry powder, and all of the powder having a particle size of 63 μm or less is applied to a stainless steel test sieve having a nominal opening of 63 μm according to JIS Z8801. It was in a state.

  In addition, for this sintering, a gas pressure sintering apparatus was used, and the sample was placed in a container with a boron nitride lid, which was accommodated in the gas pressure sintering apparatus, and in a nitrogen atmosphere, the pressure was 1.0 MPa. Gas pressure sintering was performed. The sintering temperature at this time was 1700 ° C., and the holding time at the sintering temperature was 8 hours.

  After sintering, when it was taken out from the apparatus, it was broken into a powder by applying a slight force on the mortar. This is sample B1.

  Next, only particles having a particle size of 125 μm or less were classified and classified using a test screen sieve made of stainless steel having a nominal opening of 125 μm in accordance with JIS Z 8801, and pulverized using a planetary ball mill. In this case, a container made of silicon nitride, a grinding medium made of calcium solid solution alpha sialon, and special grade ethanol were used.

  Samples with a grinding time of 1 hour are sample B2, samples with 6 hours are sample B3, and samples with 12 hours are sample B4.

  FIG. 6 is a diagram showing excitation spectra of the remaining two samples of the eight samples used in this experiment, that is, samples C and D.

  Sample C is the same as Sample A2 except that the composition is x = 0.875, m = 1.9999, n = 0.999995, and y = 0.0833.

  Sample D is the same as Sample A2 except that x = 0.875, m = 1.96, n = 0.98, and y = 0.07.

  As shown, clear peaks are observed in samples C and D, and this result clearly indicates that it is desirable to excite the phosphor by using a blue light emitting diode of this wavelength. In addition, the excitation peak wavelength of these samples C and D is 449-450 nm.

  In the measurement of the emission spectrum and the excitation spectrum, a spectrofluorometer calibrated using the rhodamine B method and a standard light source was used. In particular, the wavelength calibration was performed within ± 2.0 nm of the 450.1 nm emission line of the xenon light source, and the deviation of the measured value was within 1 nm.

  From the above, in the Ca solid solution alpha sialon phosphor activated by divalent Eu, when the excitation peak wavelength changes over a wide range of 400 to 450 nm by post-processing after sintering and classification by particle size Turned out to be.

  Therefore, it can be said that a general judgment for those skilled in the art to use a blue light-emitting diode in accordance with the excitation peak wavelength is not valid.

  Here, the inventors focused on the inflection point at 450 nm. The fact that the excitation spectrum has such an inflection point itself is a new truth that has been elucidated by the inventors' research, and the excitation intensity is relatively strong on the shorter wavelength side than this inflection point. On the long wavelength side, it decreases rapidly.

  From this point of view, it is considered that high efficiency can be ensured by exciting in the range of 400 to 450 nm from the viewpoint of only the excitation spectrum.

  On the other hand, when the wavelength is shortened, problems such as poor visibility and significant deterioration of the sealing resin of the light emitting device occur.

In addition, the light emitting device contemplated by the present invention has a white color by mixing blue light emitted from a blue light emitting diode element and yellow fluorescence emitted by a Ca solid solution alpha sialon phosphor that has absorbed the blue light. Therefore, it is not desirable that the light emission color approaches blue to purple by using a light emitting diode element having a light emission peak wavelength on the short wavelength side. Further, currently, a blue light emitting diode element having a light emission peak wavelength of 450 nm, 460 nm or 470 nm It is also necessary to consider that it is easy to obtain.

  Considering these various factors, it can be determined that 450 nm is appropriate as the excitation wavelength.

  Further, in any of the samples A1 to A2 and the samples B1 to B4, this important inflection point exists at or near the wavelength of 450 nm, and the wavelength shift is caused even when the excitation spectrum shape changes greatly. Not done.

  From the above points and further experimental results, Ca solid solution alpha sialon phosphor satisfying 0.6 ≦ x ≦ 1.0 and 0.05 ≦ y ≦ 0.10, and Ca solid solution alpha sialon phosphor having an emission peak wavelength of Ca It has been found that a light-emitting device with improved luminance can be realized by using a blue light-emitting diode element in the range of ± 3 nm centered on the inflection point of λ, that is, 450 ± 3 nm.

  The reason why the emission peak wavelength of the blue light emitting diode element is given a width of ± 3 nm is that the variation of the emission peak wavelength that occurs during the manufacture of the light emitting diode element is taken into consideration.

Next, Non-Patent Document 1 (Xiao Zhang and Xingren Liu, “Luminescence Properties and Energy Transfer of Eu ²⁺ Doped Ca ₈ Mg (SiO ₄ ) ₄ Cl ₂ Phosphors,” J. Electrochem. Soc., Vol. 139 , No. 2, February 1992, pp. 622-625.) The reason why the inflection point appears in the range of 449 nm to 450 nm will be discussed with reference to FIG. This Ca ₈ Mg (SiO ₄₎ which is activated by ^{Eu 2+} in the literature ₄ Cl ₂ phosphor ^is excited by the parity allowed transition from the ground state to the excited state of the ^4f 6 5d of 4f ⁷ _{(8 S 7/2)} The Looking at the excitation spectrum for the emission of 507 nm, there are two excitation wavelength bands corresponding to the two excited states of the e _g and t _{2 g} of 4f 6 ^5d by division of the crystal field, low Among energy level (longer wavelength Seven smaller peaks are observed on the side. These peaks are divided into seven levels ⁷ F ₀ , ⁷ F ₁ , ⁷ F ₂ , ⁷ F ₃ , ⁷ F ₄ , ⁷ F ₅ and ⁷ F _{6 according} to the state of 4f ^6. Corresponding. According to Table I, it is considered that the excitation wavelength corresponding to the transition from 4f ⁷ ( ⁸ S _7/2 ) to 4f ⁶ ( ⁷ F ₃ ) 5d is 449 nm, and a peak is observed at 448 nm. Has been.

It is considered that the excitation spectrum of the alpha sialon phosphor of the present invention can be understood in the same manner. The excitation band of 400 nm to 450 nm corresponds to the lower energy level (on the longer wavelength side) of the two excitation wavelength bands, and a plurality of small peaks are observed in the region around 450 nm. Therefore, it is considered that the inflection point observed in the excitation spectrum of the alpha sialon phosphor from 449 nm to 450 nm corresponds to the transition from 4f ⁷ ( ⁸ S _7/2 ) to 4f ⁶ ( ⁷ F ₃ ) 5d. It is essential because it is activated by Eu ²⁺ .

<Example>
Next, examples of the present invention will be described. However, these examples are only for explaining the present invention, and do not limit the scope of the present invention. Accordingly, those skilled in the art can employ various embodiments including each or all of these elements, and these embodiments are also included in the scope of the present invention.

  In all the drawings for explaining the following embodiments, the same reference numerals are given to the same elements, and the repeated explanation thereof is omitted.

Example 1
FIG. 1 is a perspective view of a bullet-type white light-emitting diode lamp (light-emitting device) 1 according to a first embodiment (Example 1) of the present invention. FIG. 2 is a cross-sectional view of the bullet-type white light-emitting diode lamp 1. FIG.

  The bullet-type white light-emitting diode lamp 1 has a substantially cylindrical shape whose upper part is a lens-shaped spherical surface, in other words, has a shape similar to a bullet, and the emission peak wavelength that emits blue light with the lead wires 2 and 3. Is a blue light emitting diode element 5 having a wavelength of 450 nm, a bonding wire 6, a Ca solid solution alpha sialon phosphor (hereinafter referred to as “alpha sialon phosphor” as appropriate) 7 similar to the sample A2, and resins 8 and 9 The lower portions of the lead wires 2 and 3 are exposed.

  A concave portion 4 is provided at the upper end portion of the lead wire 2, and a blue light emitting diode element 5 is placed in the concave portion 4, and an electrode (not shown) provided in the lower portion and the bottom surface of the concave portion 4 are electrically conductive. An electrode (not shown) provided on the top thereof and the lead wire 3 are electrically connected by a bonding wire 6.

  Further, the vicinity of the blue light emitting diode element 5 including the recess 4 is sealed with a resin 8, and 35 wt% (weight percent) of alpha sialon phosphor 7 is dispersed in the resin 8.

  The lead wires 2 and 3, the blue light emitting diode element 5, the bonding wire 6, and the resin 8 are sealed with a resin 9.

  Resins 8 and 9 are both transparent and are the same epoxy resin.

Next, a manufacturing procedure of the above-described bullet-type white light-emitting diode lamp 1 will be described.
In the first step, the blue light emitting diode element 5 is die-bonded to the recess 4 using a conductive paste.

  In the second step, the blue light emitting diode element 5 and the other lead wire 3 are wire-bonded by the bonding wire 6.

  In the third step, the resin 8 is cured by pre-dipping the recess 4 so as to cover the blue light-emitting diode element 5 with the resin 8 in which the alpha sialon phosphor 7 is dispersed.

  In the fourth step, the upper portions of the lead wires 2 and 3, the blue light emitting diode element 5, and the resin 8 are surrounded by the resin 9 and cured. This fourth step is generally performed by casting.

  In addition, the lead wires 2 and 3 can be manufactured integrally, and in this case, they have a shape in which lower portions thereof are connected. In using such an integrally manufactured lead wire, a fifth step is provided after the step 4 in which the portion connecting the lead wires 2 and 3 is removed and the lead wires 2 and 3 are used as separate members. It is done.

(Example 2)
FIG. 3 is a perspective view of a chip type white light emitting diode lamp (light emitting device) 10 according to a second embodiment (Example 2) of the present invention, and FIG. 4 is a cross section of the chip type white light emitting diode lamp 10. FIG.

  The chip type white light emitting diode lamp 10 includes a blue light emitting diode element 5, an alpha sialon phosphor 7, an alumina ceramic substrate 11, lead wires 12 and 13, a side member 15, a bonding wire 16, and resins 17 and 18. It consists of.

  The alumina ceramic substrate 11 has a quadrangular shape and high visible light reflectivity.

  The lead wires 12 and 13 are provided on the alumina ceramic substrate 11, and end portions thereof protrude outside the alumina ceramic substrate 11.

  The other end of the lead wire 12 is located at the central portion of the alumina ceramic substrate 11, on which the blue light-emitting diode element 5 is placed, and an electrode (not shown) provided therebelow. ) And the lead wire 12 are electrically connected by a conductive paste, and an electrode (not shown) provided on the lead wire 13 and the lead wire 13 are electrically connected by a bonding wire 16.

  The phosphor 7 is dispersed in the resin 17, and the resin 17 seals the entire blue light emitting diode element 5.

  Further, the side member 15 is provided with a circular space 14 at the center thereof, and is fixed on the alumina ceramic substrate 11.

  The space 14 is for housing the blue light emitting diode element 5 and the resin 17 in which the alpha sialon phosphor 7 is dispersed, and the inner wall surface is inclined. This is a reflection surface for extracting light upward, and the curved surface shape is determined in consideration of the reflection direction of light.

  In addition, at least the surface constituting the reflective surface is made of a material having white or metallic luster and high visible light reflectivity. In this embodiment, the side member 15 is made of a white silicone resin.

  Further, the resin 18 fills the space portion 14 and further seals the resin 17 sealing the blue light emitting diode element 5.

  The resins 17 and 18 are both transparent and are the same epoxy resin.

  The manufacturing method of the chip-type white light-emitting diode lamp is substantially the same as the manufacturing method of the above-described bullet-type white light-emitting diode lamp 1 except for the step of fixing the lead wires 12 and 13 to the alumina ceramic substrate 11. .

  The above light-emitting device can exhibit high luminance due to the above-described configuration.

1 is a perspective view of a bullet-type white light-emitting diode lamp according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of the bullet-type white light emitting diode lamp of FIG. 1. It is a perspective view of the chip type white light emitting diode lamp which concerns on Example 2 of this invention. FIG. 4 is a cross-sectional view of the chip type white light emitting diode lamp of FIG. 3. It is a figure which shows the excitation spectrum of sample A1, A2, B1, B2, B3, and B4. It is a figure which shows the excitation spectrum of the samples C and D. It is a figure which shows the excitation spectrum and emission spectrum of a YAG type fluorescent substance activated by Ce. It is a figure which shows the emission spectrum of Ca solid solution alpha sialon fluorescent substance activated by Eu.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cannonball type white light emitting diode lamp 2, 3, 12, 13 Lead wire 4 Recessed part 5 Blue light emitting diode element 6, 16 Bonding wire 7 Alpha sialon fluorescent substance 8, 9, 17, 18 Resin 10 Chip type white light emitting diode lamp 11 Alumina Ceramic substrate 14 Space 15 Side member

Claims (4)

A blue light emitting diode element;
A calcium solid solution sialon phosphor activated by divalent europium ions,
The inflection point of the excitation spectrum of the calcium solid solution sialon phosphor is in the blue wavelength region of the excitation spectrum measured using the emission peak wavelength as the monitor wavelength,
The light emitting device has a light emission peak wavelength within a range of ± 3 nm centered on the inflection point. 2. The light emission according to claim 1, wherein the inflection point is an excitation wavelength corresponding to a transition from a 4f ⁷ ( ⁸ S _7/2 ) ground state to a 4f ⁶ ( ⁷ F ₃ ) 5d excited state. device.   The light emitting device according to claim 2, wherein the inflection point is 449 nm to 450 nm. The composition of the calcium dissolved SiAlON phosphor has the general formula _{Ca x Si 12- (m + n} ) Al (m + n) O n N 16-n: is represented by _{^{Eu 2+ y, 0.6 ≦ x ≦}} 1.0 and 0 .05 ≦ y ≦ 0.10,
The light emitting device according to claim 1, wherein an emission peak wavelength of the light emitting diode element is in a range of 450 ± 3 nm.

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